Sefety device for an explosive-operated powor tool



ER TOOL W. BELL.

Jan. 2, 1969 SAFETY DEVICE FOR AN EXPLOSIVEOPERATED POW Sheet Filed April s, 196e W. BELL Jan. 21, i969 SAFETY DEVICE FOR AN EXPLOSIVE-OPERATED POWER TOOL Sheet United States Patent O 3,423,001 SAFETY DEVICE FOR AN EXPLOSIVE-OPERATED POWER TOOL Walter Bell, Monroe, N.Y., assignor to Star Expansion Industries Corporation, Mountainville, N.Y., a corporation of Delaware Filed Apr. 5, 1966, Ser. No. 540,381 U.S. Cl. 227-8 Int. Cl. B25c 1/10 3 'Claims ABSTRACT F THE DISCLOSURE This invention relates to power-actuated tools. More particularly, this invention relates to an explosive-actuated tool for driving fasteners and the like.

Explosive-actuated tools for driving fasteners are wellknown in the art and are widely used. In general, such tools comprise a housing of pistol-like form comprising a grip with an associated trigger and a generally tubular forward portion, a barrel mounted within the tubular forward portion of the housing and adapted to move axially therein, and a piston contained within the barrel and adapted to move axially with respect to the barrel.

In the usual form of such tools, the breech end of the barrel is recessed to form a chamber for an explosive cartridge, the chamber communicating with the bore so that the gases generated by the explosive charge are transmitted to the face of the piston; and a more or less conventional ring mechanism including a firing pin is located in the housing.

In the operation of the tool, the barrel is moved forward with respect to the housing, and a cartridge is inserted in the chamber. A fastener or the like is positioned. in the muzzle end of the barrel, forward of the piston. The barrel is then moved rearwardly with respect to the housing, bringing the chamber into proximity with the firing pin; and also, by way of suitable operating rods, cams, or the like, cooking the ring mechanism. As a safety feature, it is common to provide that the ring mechanism is cocked by moving the barrel rearwardly against a substantial spring bias, generated by pressing the -muzzle of the tool against the surface into which the fastener is to be driven.

While the tools of this general type heretofore proposed have been effective and have obtained wide acceptance, they are nevertheless subject to certain disadvantages, or areas susceptible of improvement.

In particular, the above-mentioned safety feature, whereby the action is cocked by moving the barrel rearwardly against a spring bias, is susceptible of being accidentally rendered inoperative; or can intentionally be made inoperative simply by moving the barrel rearwardly, and thereby cooking the action in some manner other than by pressing the end of the barrel forcibly against a surface into which a fastener is to be driven.

For example, when working in close quarters, the situation may sometimes arise where the muzzle of the tool can be brought close to the surface in -which a fastener is to be driven, but because of interference of adjacent structural parts cannot be brought in contact with the surface or pressed against it to cock the tool. Under these circum- ICC stances, the operator may be tempted to cock the action by grasping the muzzle end of the barrel and moving it back by hand, and to shoot the fastener into the surface from a position slightly removed therefrom. This results in the fastener being incompletely or improperly driven. Moreover, if the clearance between the muzzle and the surface at the time of tiring exceeds the length of the fastener, the latter may ricochet off the surface into free flight, constituting a serious safety hazard.

Moreover, having discovered that the tool may be cocked and fired in a manner other than by pressing it against a wall or the like, the operator or others may be tempted to use the tool improperly, for example, for target practice, horseplay, or even as a fairly effective shortrange weapon.

An object of this invention, therefore, is to provide an improved explosively-actuated power tool.

Another object is to provide an explosively-actuated power tool having a housing and a barrel axially movable relative to said housing, characterized by improved means for controlling the relative position of said barrel with respect to said housing.

Still another object is to provide a tool of the type described, having improved safety means for the prevention of accidental or intentional improper firing thereof.

A feature of the invention is the use of a barrel movable rearwardly to cock the action, said barrel being provided with means for preventing said barrel from being so moved in any manner other than by axial pressure exerted directly on the muzzle thereof.

Another feature is the provision of a sleeve around said barrel adjacent the muzzle end thereof, said sleeve being free to move axially of said barrel.

According to another feature, the collar is provided with a spring positioned to urge the sleeve toward the muzzle end of the barrel.

Another feature is the provision of an enlarged portion of said barrel adjacent the muzzle end thereof, said en.- larged portion providing an abutment to limit the forward motion of the sleeve with respect to the barrel.

According to another feature, the barrel is urged forwardly with respect to the housing by a first spring; and the sleeve is urged forwardly with respect to the barrel by a second spring, said second spring being yieldable in response to a substantially smaller applied pressure than said rst spring.

Another feature is the provision of abutment means associated with the housing for limiting the rearward motion of the sleeve with respect to the housing.

Other objects, features and advantages will become apparent from the following more complete description and claims, and the accompanying drawings.

In one particularly desirable embodiment, this invention contemplates a safety device for an explosive-operated power tool of the type having a housing, an axially movable barrel, and a ring mechanism designed to be cocked by pressing the muzzle of said barrel against a surface and thereby moving said barrel rearwardly with respect to said housing, said safety device comprising in cornbination a sleeve surrounding at least a major part of said barrel in the region extending from the muzzle end thereof to the forward end of said housing when said tool is in the uncocked condition, said sleeve being axially movable with respectfto said barrel, and means for limiting the reanward motion of said sleeve with respect to said housing.

Referring now to the drawings:

FIGURE 1 is a side elevation of an explosive-actuated power tool equipped with a safety device according to the invention;

FIGURfE 2 is a front view of the tool of F'IGUR'E 1;

FIGURE 3 is a medial longitudinal cross-section of the tool of FIGURES 1 and 2, taken along the line 3 3 of FIGURE 2, and showing the disposition of parts when the tool is in the uncooked conditon;

FIGUR-E 4 is a fragmentary cross-section similar to the corresponding portion of FIG-URE 3, showin-g the effect of an attempt to cock the firing mechanism by drawing lbac'k -manually on the sleeve of the safety device;

FIGURE 5 is a cross-section similar to FIGURE 3, showing the disposition of the parts 'when the action is properly cocked by pressing the muzzle of the tool against a surface into which a fastener is to be driven;

FIG-URE 6 is an exploded view, partly in section, of the safety device according to the invention, together with asociated parts of the tool; and

FIGURE 7 is a birdseye perspective of the muzzle portion of a tool equipped with the safety device according to the invention.

Referring now more particularly to FIGURE 3, the tool as there illustrated comprises a housing, indicated generally at 10, comprising a pistol grip 12, a breech section 14, and a generally tubular forward section 16. Housed in the forward section 16 is a barrel which is free to move axially Iwithin the housing. In the illustrated form of the invention, the barrel is made in Jcwo sections, namely, a main section 20 and a muzzle section 22. The main section 20 is provided with a central axial bore 24 and a muzzle piece 22 with a somewhat narrower bore 26, see FIGURES 4, 5, 6, and 7. A collar 122 having internal threads 122g is mounted on the threaded end 22a of the muzzle piece 22 and is fixedly secured in position, as by being keyed thereto after the assembly of sleeve 124 and spring 112 therewith. The safety device 126 is thus constituted as a unit struct-ure which is removably mounted on the forward end of main barrel section 20 by means of the external threads 1221) on collar 122.

Within barrel 20 is housed a piston 28 having three cylindrical portions 30, 32 and 34 of relatively increasing diameter in the order named. The diameter of piston section 30 is sized to t closely, but slidably, within the bare 26 of the muzzle piece; and that of piston section 34 is sized to form a sliding but substantially gas-tight fit in the bore 24 of main barrel section 20.

.T he breech end of barrel main section 20 is chambered to accommodate an explosive cartridge 36, and bored to provide a gas passage 38 communicating with bore 24. The breech end is also provided with slot 40.

Projecting axially and reanwardly from the breech end of barrel main section 20 is a cocking rod 78.

Near the for-Ward end of housing fonward portion 16 is a threaded aperture 44 adapted to receive a threaded plug 46. Plug 46 is recessed to receive the cylindrical base of a key 48. The rectangular upper portion of key 48 projects upwardly into bore 24, through an axial slot 40 provided for the purpose in barrel main section 20.

The juncture bet-Ween the lower cylindrical portion and the upper rectangular portion of key `48 provides a pair of segment-shaped shoulders 52 positioned to bear against the surface of barrel main section 20'. The lower cylindrical portion of key 48 is recessed to receive a compressible member such as a plug 54 of rubber or the like. The head of plug 46 is preferably slotted or knurled or both; and the pressure wit-h which shoulders 52 bear against the barrel is adjusted by turning down the plug, there by increasing the compression of resilient member 54, which compression is transmitted to key 48.-

The upper rectangular portion of key 48 projects into bore 24 sufficiently far to intercept the maximum diameter portion 34 of the piston, but not so far as to intercept the intermediate diameter portion 32.

The function of the frictional force exerted by shoulders 52 on main barrel section 20 is to yieldingly restrain the barrel against movement relative to the housing. This helps to avoid unnecessary wear and facilitates handling and operation of the tool, because the barrel tends to remain in whatever position the operator has placed it,

4 while other operations are performed, such as loading, etc.

The function of the upper rectangular portion of key `43 is twofold. First, as the barrel is moved forward relative the housing, for example, to the forward or loading position, the upper portion of key 418 intercepts maximum diameter section 34 of the piston and prevents the piston from going fonward with the barrel. Thus, as the barrel moves forward and the piston remains stationary Irelative to the housing, the piston is moved all the Iway to the rear of bore 24, in proper position for firing. The same motion clears bore 26 in the muzzle piece for the insertion of a fastener to be driven.

The second function of the rectangular portion of `key 4-8 is to limit the forward motion of the barrel. When the barrel reaches the extreme fon-ward or loading position, further forward motion of the piston is prevented by abutment of maximum diameter piston section 34 against the key; and further forward motion of the barrel is prevented by abutment of the Irear end of bore 20 against the rear face of piston section 34. In the illustrated form of the invention, if Ikey 48 were not present, the barrel would be free to move completely out of the housing; and the tool is, in fact, disassembled for cleaning and servicing by removing plug 46 and key 48, allowing the barrel to be removed.

The normal operation of the tool is as follows. The barrel is first moved forwardly manually or by throwing the tool to create a forward centrifugal force. This moves the piston to the rear of the barrel by the action of key 48, as described abo-ve. The tool is inverted, if necessary, sufficiently to drop the spent cartridge out through loading aperture in the housing. A fresh cartridge 36 is inserted through loading aperture 100, into the chamber provided in the breech end of barrel 20, and the barrel is returned manually or by pushing it against a suitable surface to the ready position shown in FIG- URE 5.

A fastener 102 (see FIGURE 5) is inserted in the muzzle piece, and the action is cocked by pushing the muzzle piece forcibly against the surface into which the fastener is to be driven, thus causing cocking ro-d 78 to push sear 80 and the firing pin back against the bias of firing pin spring 84, as shown in FIGURE 5. The trigger is squeezed, lifting Sear 80 olf cocking rod 78 and allowing the firing pin to spring forward and re the cartridge. Expanding gases from the cartridge pass through gas passage 38 and drive the piston forward, driving the fastener before it into the wall or other surface into which it is to be driven.

The forward motion of the piston is arrested by the `striking of the intermediate diameter portion 32 of the piston against the front end of bore 24, or preferably against a resilient member 104 located therein. The relative sizes of the parts are so selected with reference to the fastener that impingement of piston section 32 against resilient member 104 prevents overdriving the fastener. The tool is then taken away from the wall, the barrel moved forward to the load position, and the cycle repeated for the next fastener.

The safety device 126 according to the present invention comprises a sleeve member 124 having a major diameter portion 106 having an internal diameter sized to provide a sliding t over the forward end of barrel portion 20; and a minor diameter portion 108 having an internal diameter sized to provide a sliding t over the adjacent part of barrel member 22. The major and minor diameter portions of the sleeve member are connected -by a connecting portion 110 of any convenient shape, for example, the truncated conical shape shown in the drawings.

The sleeve is urged forwardly relative to the barrel by a compression spring 112, bearing at its forward end against a suitable abutment 114 provided by the internal configuration of the sleeve, and at its rearward end against the forward end of collar 122. The forward bias provided to the sleeve by spring 112 is countered by an enlarged portion 116 of the barrel muzzle portion 22, which serves as an abutment for the leading edge of minor diameter sleeve portion 108.

A suitable annular recess or clearance 118 is provided between the forward end of barrel portion 20 and the surrounding portion of the housing 16, into which the rearward edge of major diameter sleeve portion 106 may enter to a limited extent. The extent of such entry is limited by the depth of recess 118, which terminates in a shoulder 120 ser-ving as an abutment for the rearward edge of major diameter sleeve portion 106, thereby limiting the extent of rearward motion of the sleeve relative to the housing member.

The operation of the safety device according to the invention is as follows.

In the normal and proper use of the tool, as illustrated in FIGURES 3 and 5, the sleeve is held by spring 112 in a forward position relative to the barrel, so that the leading edge of minor diameter sleeve portion `108 abuts against the enlarged portion 116 of barrel portion 22. When the firing mechanism is cocked by pushing the muzzle against a wall or other surface into which a fastener is to be driven, the barrel is thereby moved rearwardly relative to the housing, causing cocking rod 78 to push sear 80 rearwardly against the bias of firing pin spring 84, to a point at which the sear overlies the searlifting portion of the trigger, as shown in FIGURE 5. The clearance between the rearward edge of major diameter sleeve portion 106 and the shoulder 120 forming the termination of annular recess 118 must be sufficient to allow this much rearward motion of the barrel to take place. When the trigger is squeezed, it lifts sear 80 off the end of cooking rod 78, allowing the Sear and the firing pin to spring forward under the bias of tiring pin spring 84, in the usual manner, thus ring cartridge 36 and driving the fastener.

When, on the other hand, an attempt is made to cock the tiring mechanism in a manner other than by pressing the muzzle forcibly against a rigid surface, such as a wall or the like, the safety device of the invention prevents such cocking in the manner indicated in FIGURE 4. When it is attempted to cock the action by grasping the sleeve and pulling it rearwardly, the sleeve moves rearwardly to a limited extent, compressing spring 112. Spring 112 should be of such a nature that it yields under a substantially smaller applied compressive force than ring pin spring 84, so that the compression of spring 112 -does not produce any appreciable rearward motion of the barrel and associated cooking rod 78. Excessive rearward motion of the sleeve is prevented by the limiting effect of shoulder 120, which prevents the sleeve from being drawn back in this manner lby more than a limited predetermined extent, insuicient to cock the action. This limiting effect is also advantageous in that it ensures that even when the sleeve is drawn back to its full extent, it does not expose a sufficient portion of the barrel to allow the same to be effectively grasped. This contributes further to the safety of the device, as it precludes the possibility of drawing the sleeve back to expose the underlying portion of the barrel, and then drawing the barrel back manually to cock the firing mechanism.

It will be noted, on comparing FIGURES 3 and 4, that the distance A from the muzzle end of the barrel to the leading end of the housing remains unchanged when the sleeve is pulled back as far as it can be, thus precluding any possibility of cocking the firing mechanisrn by drawing back on the sleeve.

While this invention has been described in terms of certain preferred embodiments, and illustrated by way of certain drawings, these are illustrative only, as many alternatives and equivalents will readily occur to those skilled in the art, Without departing from the spirit or proper scope of the invention. The invention is, therefore, not to be construed as limited, except as set forth in the appended claims.

I claim:

1. A safety device -for an explosive-operated power tool of the type having a housing, an axially movable barrel and a firing mechanism designed to be cocked by pressing the muzzle of said barrel against a surface and thereby moving said barrel rearwardly with respect to said housing, said barrel further comprising a main section and a muzzle section, said safety device comprising in combination a sleeve surrounding at least a major part of said barrel in the region extending from the muzzle end thereof to the forward end of said housing when said tool is in the uncooked condition, said sleeve 4being axially movable with respect to said barrel, said sleeve further comprising a member having a major diameter portion having an internal diameter sized to provide a sliding lit over the forward end of said main section of said barrel and a minor diameter portion having an internal diameter sized to provide a sliding t over the adjacent part of said muzzle section of said barrel, the major and minor diameter portions of the sleeve member being joined by a connecting portion with the result that said connecting portion effects a generally truncated conical shape, means for limiting the rearward motion of said sleeve vw'th respect to said housing, said sleeve being urged forwardly with respect to said barrel by a spring, said spring being yieldable under an applied force insufficient to cock said firing mechanism.

2. A safety device for an explosive-operated power tool of the type having a housing, an axially movable barrel and a tiring mechanism designed to be cocked by pressing the muzzle of said barrel against a surface and thereby moving said barrel rearwardly with respect to said housing, said barrel further comprising a main section and a muzzle section, said safety device comprising in combination a sleeve surrounding at least a major part of said barrel in the region extending from the muzzle end thereof to the forward end of said housing when said tool is in the uncocked condition, said sleeve being axially movable with respect to said barrel, said sleeve further comprising a member having a major `diameter portion having an internal diameter sized to provide a sliding fit over the forward end of said main section of said barrel and a minor diameter portion having an internal diameter sized to provide a sliding fit over the adjacent part of said muzzle section of said barrel, the major and minor diameter portions of the sleeve member being joined by a connecting portion with the result that said connecting portion effects a generally truncated conical shape, means for limiting the rearward motion of said sleeve with respect to said housing, the forward motion of said slee-ve with respect to said barrel being limited by an enlarged portion of said barrel adjacent the muzzle end thereof.

3. A safety device according to claim 3, wherein said sleeve and said housing cooperate to surround substantially all of said barrel other than said enlarged portion when said tool is in the cocked condition.

References Cited UNITED STATES PATENTS 2,925,603 2/ 1960 Pfaff et al. .-227-8 2,945,236 7/ 1960 Kopf et al. 227-8 3,038,159 6/ 1962 Helderman 227-8 3,075,197 1/1963 Kissane 227-8 3,248,032 4/1966 Bochman 227-8 3,348,751 10/1967 Henning 227-8 TRAVIS S. MCGEHEE, Primary Examiner.

ROBERT L. FARRIS, Assistant Examiner. 

